Add emulation of IBM PS/1 Model 2121.

As part of this :
- FDC Specify command now completes immediately
- Implemented keyboard system flag status
- Added ability to remap 384kb reserved memory to above extended memory

src/Makefile.mingw

@@ -16,7 +16,7 @@ OBJ = 386.o 386_dynarec.o 386_dynarec_ops.o 808x.o acer386sx.o ali1429.o amstrad
 	vid_ati28800.o vid_ati68860_ramdac.o vid_cga.o vid_cl5429.o vid_ega.o vid_et4000.o \
 	vid_et4000w32.o vid_et4000w32i.o vid_hercules.o vid_icd2061.o vid_ics2595.o vid_incolor.o vid_mda.o \
 	vid_olivetti_m24.o vid_oti067.o vid_paradise.o vid_pc1512.o vid_pc1640.o vid_pc200.o \
-	vid_pcjr.o vid_s3.o vid_s3_virge.o vid_sdac_ramdac.o vid_stg_ramdac.o vid_svga.o \
+	vid_pcjr.o vid_ps1_svga.o vid_s3.o vid_s3_virge.o vid_sdac_ramdac.o vid_stg_ramdac.o vid_svga.o \
 	vid_svga_render.o vid_tandy.o vid_tandysl.o vid_tgui9440.o vid_tkd8001_ramdac.o vid_tvga.o vid_unk_ramdac.o \
 	vid_vga.o vid_voodoo.o video.o wd76c10.o win.o win-config.o win-d3d.o win-d3d-fs.o win-ddraw.o \
 	win-ddraw-fs.o win-deviceconfig.o win-hdconf.o win-joystick.o win-keyboard.o win-midi.o win-mouse.o \